The eye is an amazing animal organ that is capable of converting waves of light into signals that the brain understands, in turn conveying an image to a person. It is also an extremely complex organ. Learning the basic parts of the eye can help people understand conversations with an ophthalmologist, or eye doctor, and will also assist with illustrating how the the organ works.
Working from the outside in, at the surface of the eye is the cornea. The cornea is a transparent, soft layer that covers the delicate and complex layers underneath. Damage to the cornea will impair a person's vision, but it is also one of the fastest healing parts of the body. Underneath the cornea is the sclera, or white of the eye, along with the iris and pupil. The iris is the colored portion, while the pupil is the dark area in the middle of the iris. The pupil expands and contracts to admit light to the back of the eye.
Behind the iris and pupil is the lens. The lens focuses light, directing it through the vitreous humor to the retina. The vitreous humor is a viscous fluid that fills the space between the front and back of the eye, protecting the delicate optic nerve and retina in the back and helping the eye to retain its shape. The retina is the light sensitive area in the back of the eye that is equipped with several structures that help translate the light focused through the lens into an image.
The two commonly known receptors in the retina are the rods and cones. Rods are extremely sensitive to motion and are concentrated along the edges of the retina. The rods are responsible for night vision, as they are more sensitive to subtle changes in light that can translate into shapes and peripheral movement. Cones account for the ability to see in color, and they are closely concentrated in the middle of the retina, the area called the fovea. The fovea is located at the center of the field of vision, and it is covered by the macula.
The numerous photo receptors of the eye are connected to an assortment of nerves and blood vessels which all ultimately connect to the optic nerve. This vital part connects with the brain, sending a series of electrical signals that the brain interprets as an image. Because of the way in which light is filtered through the eye, images of what a person sees actually arrive upside down, and the optic nerve flips them right side up so that the viewer can correctly understand what is going on.